The present invention relates to LED lighting technologies and particularly pertains to a white LED lamp secondary encapsulation structure which is capable of reducing blue-light hazards.
White Light-Emitting Diodes (WLEDs) are described as the “fourth generation” light sources. They are new solid-state lighting components developed in recent decades. In comparison to existing light sources (incandescent lamp, fluorescent lamp etc.), they have many significant advantages, such as energy-saving, small size, long lifespan, vibration-proof, quick responsiveness and absence of harmful substances such as mercury. The application scopes in which they are currently implemented include indoor lighting, lighting inside transportation means such as trains, ships, planes and so on, flashlight, LCD backlight (vehicles, stereos instrument panels, back light panels of mobile phones etc.), traffic lights, marker lights, messages displays, etc. The ultimate goal of their application is to replace traditional light sources.
A more popular and mature application currently in use is a white LED encapsulation technology: by covering YAG yellow fluorescent powder over a fixed blue-light chip, encapsulation is done with no space between the fluorescent powder and the chip. After encapsulation, an outer cover is provided to form an LED light. The blue light excites the fluorescent powder in short range to emit yellow light; the blue and yellow lights are transformed into polychromatic white light. With continued development and pursuit of better brightness, the luminous efficiency of such LED lights is getting higher and higher.
However, the LED lights of traditional structure have some inherent problems:
1. The point source of light results in poor photochromic uniformity and makes people feel blinded. At present, the common practice is the use of a sandblasted light-permeable cover for emitting softer light, but this practice sacrifices some luminous intensity, thus resulting in lower luminous efficiency, limited emission angle, and poor uniformity and consistency as proportion of blue light in the white light would not be lowered.
2. Since the temperature generated by the operating current continues to rise, the luminous efficiency of fluorescent powder would also decline sharply; meanwhile, the emission peak is wide and short, the blue light excitation peak is high and narrow, the wavelength is short and the energy is high, so that it can directly penetrate the lens and reach the retina at the back of the eyes, thus activating cellular oxidizing reaction and initiating apoptosis, leading to retinal cell damage, decreased vision or even vision loss. People have already been alarmed by the possible damages to human eyes caused by LED blue light leakage.